In manufacturing semiconductor devices, various types of thermal processing apparatuses are used for conducting various kinds of processes, such as an oxidation process, a diffusion process and a CVD (Chemical Vapor Deposition) process, to an object to be processed, such as a semiconductor wafer. As one of such thermal processing apparatuses, a vertical (type of) processing apparatus is used, which is capable of conducting a thermal process to a large number of objects to be processed at one time.
A vertical thermal processing apparatus comprises, generally, a processing container made of quartz that contains a objects to be processed, a main heater provided so as to surround the processing container, the main heater being capable of heating the processing container and having a rapid cooling function, a gas-discharging part formed at an upper portion of the processing container, the gas-discharging part being bent to connect to a discharging pipe, and an auxiliary heater provided so as to heat the gas-discharging part (for example, refer to Japanese Patent Laid-Open Publication No. 2003-209063). An opening part is formed at a lower portion of the processing container, and a lid is provided so as to be capable of moving up and down (be capable of opening and closing) so as to close the opening part. A boat made of quartz that holds objects to be processed in a tier-like (multistage) manner is provided at an upper portion of the lid.
According to the above-described vertical thermal processing apparatus, it can be rapidly heated up and rapidly cooled down, because a thermal capacity of the processing container is smaller in comparison with a thermal processing apparatus that has a processing container having a double tube structure with a large thermal capacity. Therefore, a certain improvement in throughput thereof can be expected. Additionally, because the gas-discharging part is heated by the auxiliary heater, it is possible to restrain a processing gas component from adhering to an inner surface of the gas-discharging part and forming a film thereon.
Incidentally, in the above-described vertical thermal processing apparatus, after a thermal processing (process) is finished and the objects to be processed are taken out of the boat, only the boat is conveyed into the processing container and the lid is closed. Next, in this state, the processing container is cooled down to a predetermined temperature, for example, a normal temperature by making use of a rapid cooling function of the main heater, and a cleaning gas (such as an etching gas) is introduced into an inside of the processing container, so that an inner surface of the processing container and the boat are dry-cleaned (dry-scrubbed).
However, in the above-described vertical thermal processing apparatus, the auxiliary heater does not have the rapid cooling function. Therefore, it is difficult to cool down the gas-discharging part as rapidly as the processing container (the main body). Consequently, a film may remain on an inner surface of the gas-discharging part, and this may cause particles. In addition, there is a problem; because it needs a long time for the gas-discharging part to be cooled down to the same temperature as that of the processing container (the main body), a waiting time during operation of the apparatus or a downtime during maintenance thereof are made longer, and therefore this will be an obstacle to the improvement in throughput and the improvement in productivity.